MADRID, Sept 29 (Reuters) - Spain's Ebro Puleva , one of the world's biggest rice processors, said on Friday it suspended rice imports from the United States in August after detecting genetically modified grain in a shipment.

"We have suspended imports from the USA since August 18," the company said in a statement.

"The detection of GMO rice was a complete surprise to us and we regret having to take this decision due to the close ties we have with that country (the United States)," it said.

"We are importing from other countries, except for China, which also uses transgenic seeds," a company spokeswoman said.

Ebro Puleva did not say how much rice it usually imports from the United States, but said it mainly bought U.S. rice to send to northern Europe and supplied the Spanish market from production in Seville.

No biotech rice is allowed to be grown, sold or marketed on the territory of the European Union's 25 countries.

In August, the European Commission tightened rules governing imports of U.S. long-grain rice to prove the absence of the LL Rice 601 strain, which it said was marketed by Germany's Bayer AG and produced in the United States.

Its decision followed the discovery by U.S. authorities of trace amounts of the GMO rice, engineered to resist a herbicide, in long-grain samples that were targeted for commercial use.